Observation of $Ξ_c(2930)^0$ and updated measurement of $B^-→K^-Λ^+_c\bar{Λ}^-_c$ at Belle

• Published in: The European physical journal. C, Particles and fields Vol. 78; no. 3
• Main Authors: Shen, C. P., Adachi, I., Ahn, J. K., Aihara, H., Al Said, S., Asner, D. M., Aushev, T., Ayad, R., Babu, V., Badhrees, I., Bakich, A. M., Behera, P., Biswal, J., Bonvicini, G., Chekelian, V., Chen, A., Chilikin, K., Cho, K., Choi, S. -K., Cinabro, D., Dash, N., Di Carlo, S., Drásal, Z., Eidelman, S., Epifanov, D., Fast, J. E., Ferber, T., Fulsom, B. G., Gabyshev, N., Garmash, A., Gelb, M., Guido, E., Haba, J., Hara, T., Hayasaka, K., Hayashii, H., Inami, K., Ishikawa, A., Iwasaki, Y., Jacobs, W. W., Jia, S., Jin, Y., Karyan, G., Kichimi, H., Kiesling, C., Kim, J. B., Kim, K. T., Kinoshita, K., Kodyš, P., Korpar, S., Križan, P., Kroeger, R., Kulasiri, R., Lee, S. C., Li Gioi, L., Liventsev, D., Lubej, M., Luo, T., Matsuda, T., Merola, M., Mizuk, R., Moon, H. K., Mrvar, M., Mussa, R., Nakano, E., Nakao, M., Nayak, M., Niiyama, M., Nishida, S., Pakhlov, P., Pakhlova, G., Park, C. W., Park, H., Paul, S., Piilonen, L. E., Russo, G., Sakai, Y., Santelj, L., Schneider, O., Schnell, G., Shibata, T. -A., Shwartz, B., Sokolov, A., Solovieva, E., Starič, M., Sumiyoshi, T., Tamponi, U., Tanida, K., Uchida, M., Unno, Y., Van Hulse, C., Varner, G., Waheed, E., Wang, C. H., Wang, M. -Z., Won, E., Yelton, J., Zhang, Z. P., Zhukova, V., Zhulanov, V.
• Format: Journal Article
• Language: English
• Published: United States Springer 23-03-2018
• Subjects: PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
• ISSN: 1434-6044

Here, we report the first observation of the $Ξ_c(2930)^0$ charmed-strange baryon with a significance greater than 5σ. The $Ξ_c(2930)^0$ is found in its decay to $K^-Λ^+_c$ in $B^-→K^-Λ^+_c\bar{Λ}^-_c$ decays. The measured mass and width are $[2928.9±3.0(stat.)^{+0.9}_{-12.0}(syst.)]$ MeV/ $c^2$ and $[19.5±8.4(stat.)^{+5.9}_{-7.9}(syst.)]$ MeV, respectively, and the product branching fraction is $\mathcal{B}(B^-→Ξ_c(2930)^0\bar{Λ}^-_c)\mathcal{B}(Ξ_c(2930)^0→K^-Λ^+_c)=[1.73±0.45(stat.)±0.21(syst.)]×10^{-4}$. We also measure $\mathcal{B}(B^-→K^-Λ^+_c\bar{Λ}^-_c)=[4.80±0.43(stat.)±0.60(syst.)]×10^{-4}$ with improved precision, and search for the charmonium-like state Y(4660) and its spin partner, Yη, in the $Λ^+_c\bar{Λ}^-_c$ invariant mass spectrum. No clear signals of the Y(4660) nor its spin partner are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of (772±11)×106B B ¯ pairs collected at the Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron–positron collider.